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Pad Mounted Xformer as Step upp transformer

Pad Mounted Xformer as Step upp transformer

Pad Mounted Xformer as Step upp transformer

(OP)
I need to step up a 2MW 480VAC standby diesel generator to 13.2kV in order to tie it into an existing 13.2kv system via and open transition MV auto transfer switch.  

I also want to have this 2500kVA transformer available as a spare in the event one of the two normal source pad mounts should fail.  Since the normal source transformers are 13.2kV/4800-277 D/Y with some 4 wire loads, I am thinking that the step up transformer will need to be wound Y/Y

Questions:

1. Is a pad mounted transformer suited for generator step up duty?

2. Are there any issues having a Y/Y step-up feeding a D/Y step down when the generator is in use and the utility is off.

3. Can the Y/Y replace the D/Y as the utility source step down in the event a D/Y fails?

4. I assume losses in the step-up step down scheme. Is there a factor to use to up size the generator in this application?

Any and all other comments on this scheme will be appreciated.

Thanks

RE: Pad Mounted Xformer as Step upp transformer

1. Yes, but you need to evaluate internal fusing, bonding jumpers and tap changers if present.
2. Hard to say.
3. It depends on your grounding and protective relaying schemes. I wouldn't bet on it. The transformer configuration can completely change your protection requirements. Keep in mind the delta-wye has a 30 deg phase shift.
4. Losses would be at most a few percent. I would be more concerned about voltage regulation due to the increased impedance in the circuit.

Based on the number and type of questions, I'd strongly recommend hiring a licensed engineer to evaluate this before making any purchase decisions.

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